When dealing with private and confidential information there is frequently a need to ensure that the information is kept private and confidential until a specific time, for example for seal bids the originator of a bid needs to be confident that their bid is not disclosed until a specific date.
It is an object of the present invention to facilitate the release of confidential information at (or possibly after) a specific time.
One known approach for maintaining the confidentiality of data is the use of encryption. However, traditional encryption techniques, such as the use of symmetric keys or PKI encryption, require that an appropriate decryption key is known at the time of encryption. Therefore, to ensure confidentiality the decryption key must be securely stored until required. Should, however, someone obtain unauthorised access to the decryption key this could allow unauthorised access to the confidential data. Further, the setting up and use of symmetric keys and PKI encryption can be complex.
A more recent cryptographic schema is Identifier-Based Encryption (IBE). In this schema, a data provider encrypts payload data using an encryption key string and public data provided by a trusted authority; the data provider then provides the encrypted payload data to a recipient who decrypts it using a decryption key provided by the trust authority together with the latter's public data. The trusted authority's public data is derived by the authority from private data using a one-way function. Features of the IBE schema are that any kind of string (including a name, a role, etc.) can be used as an encryption key string, and that the generation of the decryption key is effected by the trust authority using the encryption key string and its private data, enabling the generation of the decryption key to be postponed until needed for decryption.
A number of IBE algorithms are known, including the “Quadratic Residuosity” (QR) method described in the paper: “An Identity Based Encryption Scheme based on Quadratic Residues”. C. Cocks Communications-Electronics Security Group (CESG), UK. Other IBE algorithms are known such as the use of Weil or Tate pairings—see, for example: D. Boneh, M. Franklin—Identity-based Encryption from the Weil Pairing. Crypto 2001-2001.